Formation of cast-in-place concrete piles



Dec. l, 1970 L, J, PHARES; 3,543,525

FORMATION OF CAST-IN PLACE CONCRETE PILES Filed Nov. 27, 1968 '0A/056V d. Ref/425s United States Patent O U.S. Cl. 61-53.66 6 Claims ABSTRACT OF THE DISCLOSURE Use of double shells with a vibrator driver selectively clamped to one and both of the shells at different times during driving of the shells into the earth, extraction of the inner shell with a core of earth and extraction of both shells after pouring of concrete to improve the manufacture of a concrete pile.

This invention relates to the formation of cast-inplace concrete piles, and more particularly it concerns novel techniques involving the selective application of vibrations to double walled tubular shells for installing cast-in-place concrete piles.

Concrete piles are formed by excavating a hole in the earth and lining the hole with a tubular shell. Concrete is poured into the shell and the shell may be left in place or extracted depending upon whether the pile is to be cased or uncased. The shell serves to support the walls of the hole during the pouring of the concrete so that a substantially straight walled pile can be formed and so that the surrounding earth will not give way and fall into the concrete while it is being poured.

When large diameter piles are to be formed, the hole into which the concrete is to be poured cannot be practically made by simply driving a closed end shell down into it. This is because the resistance of the surrounding earth to the displacements produced by the driven plug are so great that downward movement of the plug is severely inhibited. Accordingly, attempts have been made to form the pile hole by means of a non-displacement technique wherein an open bottom tubular shell is driven down into the earth while allowing a core of earth to extend up into the center of the shell. In some cases, as described in Japanese Pat. No. 12,177/62, the tubular shell would include an inner driving tube and a closely tting outer sleeve tube. After driving, the inner tube would be withdrawn along with the core of earth.

While the open end tube arrangement did provide some advantage over the solid bottom hole forming devices, nevertheless, the earth forming the central core became compacted and eventually would form a plug so solid that the assembly became, in effect, a closed end device. Thus, the disadvantages of the closed end displacement type pile hole forming devices are not fully overcome by the use of open ended tubular shells.

The present invention overcomes the above-described difiiculties of the prior art and makes possible the formation of cast concrete piles in a far more elicient manner than has heretofore been possible. The present invention is based upon discoveries made in the course of experimenting with another invention by the same inventor, and described in U.S. Pat. No. 3,358,458. In that other invention sand drains were formed by applying vibraice tions to a double Walled tubular casing while sinking same into water bearing earth. The inner casing was removed with a core of the water bearing earth and sand was poured into the thus voided opening in the earth.

According to the present invention, a cast concrete pile is formed by the use of selectively applied vibrations in a particular manner in conjunction with double Walled tubular casings or pile shells. The process involves rst assembling the shells one inside the other and then driving the assembly down into the earth. During the driving action both shells are caused to vibrate along their length by an amount suflicient to fluidize the earth in contact with the outer surface of the outer shell as well as the earth in contact with the inner surface of the inner shell.

It as been discovered that while the application of vibrations along the length of a pile shell will lluidize the contacting earth and facilitate the driving of the shell by reduction of friction, nevertheless, the earth will tighten and lock against the shell upon the cessation of vibrations. Thus, the inner shell may be driven easily, and without the compaction of earth to form a solid plug, when vibrations are applied, and yet the inner earth core thus formed will tighten thereafter in the inner shell so that it may be removed simply by pulling the inner shell out from inside the outer shell. When the inner shell is swung away from the outer shell, it is again vibrated to loosen and release the earth core locked in it. Thereafter, concrete is poured into the outer shell and the outer shell is withdrawn. During withdrawal of the outer shell, vibrations are again applied along its length. The vibrations applied this time serve two functions, rst to uidize the surrounding earth to reduce friction and facilitate withdrawal; and secondly to assist in settling the concrete so that it Will be fully and firmly compacted in the hole.

Further specific features and advantages of the invention will be hereinafter more fully set forth with reference to the annexed drawings, showing a presently preferred embodiment of the invention and certain modications thereof, in which:

FIG. l is an elevational View partially in section illustrating a vibrator, clamp and double shell assembly entering the earth during a irst step in a pile forming operation according to the present invention;

FIG. 2 is a view showing the double shell assembly of FIG. 1 fully inserted into the earth;

FIG. 3 is a view taken along lines 3 3 of FIG. 2 and showing the extraction of the inner portion of the double shell assembly of lFIG. 1 during a second step in the pile forming operation;

FIG. 4 is a fragmentary elevational view illustrating the elimination of earth from the inner portion of the double shell assembly of FIG.- l during ya third step in the pile forming operation;

FIG. 5 is an elevational view illustrating the pouring of concrete into the doublefshell assembly during a fourth step in the pile forming operation; and

fFIG. 6 is an elevational view illustrating the extraction of the double shell assembly during a fifth step in the pile forming operation.

As shown in FIG. l, there is provided a double wall shell assembly shown generally at 10 and comprising an inner tubular shell 12 surrounded closely by an outer tubular shell 14. About the bottom edge of the outer shell 3 14, there is provided an inwardly extending lip 16 which provides a bottom covering for the small but .finite annular clearance between the inner and outer shells 12 and 14.

At the upper end of the shell assembly there is provided a vibrator and clamp assembly 18. This assembly includes a vibrator portion 20 containing internal components (not shown) constructed and arranged to generate high frequency longitudinal vibrations. The vibrator portion is connected to a pair of double action clamps 22. Each of these clamps 22 includes double acting jaw elements 24 which squeeze together on the inner and outer surfaces respectively of the inner and outer shells 12 and 14 at their upper ends. When the double action clamps 22 are in their clamped condition as shown in FIG. 1, the jaws 24 operate to squeeze together the upper edges of the inner and outer shells 12 and 14 and to transmit to both of these shells, those vibrations which are generated by the vibrator portion 20.

It will be noted from FIG. 1 that a slot 26 is formed in the upper edge of the outer tubular shell 14. A corresponding slot (not shown) is provided diametrically opposite the slot 26. As a result, by opening the clamps 22 and rotating the entire vibrator and clamp assembly 18 and thereafter reclamping the clamps 22, these clamps may be made to apply vibrations only to the inner tubular shell 12.

The entire assembly described above may be supported via an eye 28 and a cable 30 from a supporting structure (not shown) such as a derrick boom or the like.

In forming a concrete pile according to the present invention, the vibrator and clamp assembly 18 is clamped to the upper ends of the inner and outer tubular shells 12 -and 14 as shown in FIG. 1; and the entire assembly is lowered downwardly into the earth as shown. As the assembly is lowered, the vibrator portion 20 applies longitudinal vibrations along the length of both the inner and outer shells 12 and 14 as indicated by the arrows v. These vibrations serve to produce tluidization of the earth immediately adjacent the outer shell 14, as indicated at 30, and the earth immediately adjacent the inside surface of the inner shell 12, as indicated at 32. This fluidization reduces the restraining friction of the earth and facilitates the downward movement of the shells 12 and 14 into the earth. During this downward movement there is formed within the inner shell 12 a core 33 of earth. Because of the fluidization effect produced by the vibrations of the inner shell 12, the core 33 does not become compacted and driven down by the inner shell 12. Instead, the inner shell 12 moves downwardly over the core 33 allowing the core to enter up through the entire length of the shell as shown in FIG. 2.

Vibrations and driving are continued as above described until the double walled shell assembly 10 reaches maximum depth. At this point the vibrations are discontinued and the double action clamps 22 are opened. The vibrator and the clamp assembly 18 is rotated at 90i degrees so that the double action clamps 22 act through the slots 26 of the outer shell 14 and clamp again solely on the inner shell 12. The vibrator and clamp assembly 18 is then raised as illustrated in FIG. 3. During this raising the vibrator portion 20 may be operated to a certain extent in order to assist in freeing the inner shell 12 from possible frictional contact with the outer shell 14 which may have resulted from the pressures and other forces undergone during the initial driving. However, the vibrations imposed during the raising of the inner shell alone are carefully kept to a magnitude below that which would free the core 33 of earth from within the inner shell. This core, which moved freely up into the inner shell during the vibratory driving thereof, becomes locked into the inner shell when the driving vibrations cease. Thus, when the inner shell 12 is extracted as illustrated in FIG. 3, the core 33 of earth is raised up with it.

When the inner shell 12 has cleared the top of the outer shell 14 it is swung over and away from the outer shell 14 as illustrated in FIG. 4. The vibrator portion 20 is then brought into full operation to induce longitudinal vibrations along the length of the inner shell 12 thereby again producing iuidization of the earth immediately in contact with its inner surfaces. This serves to unlock the core 33 from the inner shell 12 and allow this earth to fall onto the ground away from the outer shell 14.

Following evacuation of the inner shell 14, it is returned by means of the vibrator and clamp assembly 18 to the outer shell 14 and reinserted therein. Thereafter, as shown in FIG. 5, pile forming concrete 36 is poured from a chute 38 into the inner shell 12 until the space within the inner shell 12 is completely filled. Prior to the setting of this poured concrete the vibrator and clamp assembly 18 is repositioned over the shell assembly and reclamped in a position such as to clamp the upper ends of both the inner and outer shells 12 and 14 together as illustrated in FIG. 6. At this point, the vibrator 20v is put into full operation thereby applying longitudinal vibrations to both the inner and outer shells 12 and 14. At the same time, the entire assembly is raised. The longitudinal vibrations imposed along the outer shell 14 serves to lluidize the surrounding earth thereby unlocking the shell assemblies from the earth and facilitating their withdrawal. Secondly, the vibratory action of the inner shell 12 assists in the settling of the freshly poured concrete and ensures that it becomes compacted fully into the hole formed by the double wall shell assembly. This provides a very stable and solid pile, and one which is in intimate contact with the surrounding earth.

It will be appreciated that the above-described method enables the building of cast-in-place concrete piles with a minimum of dilliculty. The selective application of vibrations to the inner and outer shells during certain steps in the performance of this method serves to make use of clamping effects which take place between the earth on the inside and on the outside surfaces of the various pile shells. It is this selective clamping and unclamping which reduces the number of steps required in the formation of the pile and which ensures maximum effectiveness of the overall pile making operation.

What is claimed is:

1. A method of forming a cast-in-place concrete pile comprising the steps of driving a double walled tubular casing formed of inner and outer shells down into the earth by direct application of vibrations to the upper end of each shell thereby causing each shell to vibrate along its length by an amount sufficient to fluidize the surrounding earth as well as an inner core of earth surrounded by the inner shell to ease penetration of the shells into the earth, withdrawing the inner shell with said inner core of earth adhered thereto while leaving said outer shell in place, pouring concrete inside the outer shell and extracting the outer shell while causing same to vibrate by an amount sufficient both to loosen the shell from the surrounding earth and to settle the poured concrete into he hole left by the lshells.

2. A method according to claim 1 wherein said inner shell, during its withdrawal with said inner core of earth, is vibrated by an amount to free it from said outer shell but insutliciently to loosen said core of earth.

3. A method according to claim 1 wherein said inner shell, after its withdrawal with said inner core of earth, is vibrated to loosen and release said core of earth away from said outer shell.

4. A method according to claim 3 wherein said inner shell is replaced inside said outer shell following the release of said core of earth and prior to the pouring of concrete.

5. A method according to claim 4 wherein said shells are vibrated together during the extraction thereof following the pouring of concrete.

6. A method according to claim 1 wherein said shells 3,303,656 2/ 1967 Landau 61-11 X are vibrated together by clamping their upper ends to- 3,358,458 12/ 1967 Phares 61-10 gether and vibrating the upper ends. 3,426,538 2/ 1969 Turzillo 61-63 X References Cited JACOB SHAPIRO, Primary Examiner 5 UNITED STATES PATENTS U'S. Cl. X R 1,249,850 12/1917 Stewart 61-53.64 61 53,5173 49 3,187,513 6/1965 Guild 61-53,5 

